US president calls on assault weapons ban and background checks hours after gun lobby ad features his two daughters.

Barack Obama, US president, has called for the reinstatement of a ban on "military-style" assault weapons and criminal background checks for gun sales as part of a $500m package of executive actions and legislative proposals aimed at reducing gun violence a month after a mass shooting in Connecticut killed 20 elementary school children.

Speaking at the White House on Wednesday, Obama signed 23 executive orders that will not require congressional approval.

Calling his reforms "common sense", Obama said that he, like most Americans, respected the US' "strong tradition of gun ownership", but that the "epidemic of violence" must be stopped.

"If there is even one thing we can do to reduce this violence. If there is even one life that can be saved, then we've got an obligation to try", Obama said as he called for aggressive new curbs on gun sales.

A presidential memorandum will instruct the Centres for Disease Control to research causes and prevention of gun violence.

In addition, Obama nominated Todd Jones as director of the Bureau of Alcohol, Tobacco, Firearms and Explosives. Jones currently is the acting director of the agency.

Obama and Joe Biden, US vice president, were accompanied at the White House event by children from across the country who wrote letters to the president about gun violence and school safety.

Al Jazeera's Patty Culhane, reporting from Washington, said the president is "hoping just to diminish gun violence ... It isn't what we've seen in Australia or the United Kingdom".

Our correspondent went on to say that Obama's proposal won't get the three million guns currently in circulation in the United States off the streets. Instead, it will limit future production of weapons.

NRA commercial

The proposal, in response to a string of shootings of the US, came hours after the National Rifle Association, the leading US gun lobby, aired an anti-gun control advertisement featuring the president's two school-aged daughters.

The narrator of the 35-second spot, aired on television and the internet, asks "are the president's children more important than yours?"

"Then why is he sceptical about putting armed security in our schools when his kids are protected by armed guards at their schools? Mr Obama demands the wealthy pay their fair share of taxes, but he's just another elitist hypocrite when it comes to a fair share of security."

Jay Carney, White House spokesman, condemned the ad, which targeted Sasha and Malia, the president's two children who attend private school in Washington, and receive Secret Service protection.

"Most Americans agree that a president's children should not be used as pawns in a political fight. But to go so far as tomake the safety of the president's children the subject of an attack ad is repugnant and cowardly."

Robert Gibbs, former press secretary for the Obama administration, called the commercial "disgusting on so many levels".

Al Jazeera's Culhane said the ad crosses an established Washington line, that the president's children are off limits, and shows that the fight around gun control "is going to become incredibly personal".

Powerful lobby

Saying his actions were not meant to be in conflict with the second amendment of the US constitution, Obama said gun reform "will not happen unless the American people demand it ... That's what it's going to take".

Notably, the president also called on residents in areas with a "strong traditon" of gun ownership to also demand that the US legislature take action on gun control.

Al Jazeera's Culhane said the president's words were a call to the southern states "who you hear as being as the NRA's base".

The support of the electorate in states that have largely been in favour of gun ownership will be of parcicular importance, said our correspondent, because the NRA is feared for being "able to get congressmen out of their jobs".